Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by some to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
Brightness is an important parameter to evaluate the performance of a display of an LCD device. A user may adjust the brightness of the display device according to the prevailing operational environment in which he/she is viewing the display device.
Referring to FIG. 9, a conventional LCD device 1 includes a liquid crystal panel 11, and a backlight module 12 disposed under the liquid crystal panel 11 for illuminating the liquid crystal panel 11.
Also referring to FIG. 10, the backlight module 12 includes a light source 121, a brightness detector 122, and a control circuit 123. The brightness detector 122 detects a brightness of ambient light of the LCD device 1, generates a corresponding photocurrent, and transmits the photocurrent to the control circuit 123. The control circuit 123 stores a plurality of reference values, the reference values having a function with photocurrent values. The control circuit 123 calculates a result according to the function of the reference values and the received photocurrent, generates a corresponding voltage signal, and adjusts the brightness of the light source 121 according to the voltage signal. Thereby, a brightness of the light beams emitted by the light source 121 corresponds with the brightness of the ambient light.
As detailed above, the LCD device 1 automatically adjusts the brightness of light provided by the backlight module 12 according to the brightness of the ambient light. However, the internal element parameters of the brightness detector 122 may change due to changes in the ambient environment such as changes in temperature. When this happens, the photocurrent generated by the brightness detector 122 does not necessarily accurately reflect the brightness of the ambient light. Further, the reference values stored in the control circuit 123 are changeless. Thus the control circuit 123 may not accurately adjust the brightness of the light source 121 to correspond with the brightness of the ambient light. Furthermore, the backlight module 12 also includes other components such as a plastic frame, a metal bottom plate, and various kinds of optical films. All together, the brightness detector 122, the control circuit 123 and the other components make the backlight module 12 rather complicated and bulky. This correspondingly makes the structure of the LCD device 1 unduly complicated and bulky.
What is needed, therefore, is a means or mechanism which can overcome the above-described deficiencies. What is also needed is a display device employing such means or mechanism.